Vulcanized rubbers

Nitrile Rubber. Vulcanized mbber sheets of NBR and montmorillonite clay intercalated with Hycar ATBN, a butadiene acrylonitrile copolymer have been synthesized (36). These mbber hybrids show enhanced reinforcement (up to four times as large) relative to both carbon black-reinforced and pure NBR. Additionally, these hybrids are more easily processed than carbon black-filled mbbers. 

There are many references in the patent literature to azo dyes prepared from 4- and 5-aminoisothiazoles, 3-, 5- and 7-amino-1,2-benzisothiazoles, and their quaternized derivatives. These are particularly useful in the dyeing of synthetic fibres. Isothiazole compounds have also been suggested for other industrial purposes, such as corrosion inhibitors, fireproofing agents, additives in rubber vulcanization, photographic chemicals and fluorescent whiteners in detergents. 

Sulfur chemistry [29] has also been used to crosslink rubber/resin PSAs, although the use of elemental sulfur itself yields tapes that can stain substrates. Other patents exemplify the use of typical rubber vulcanizing chemistry such as Tetrone A , dipentamethylenethiuramtetrasulfide, and Tuads , tetramethylthiu-ram disulfide [30], or zinc butyl xanthate [31] for this purpose. Early art [32] also claimed electron beam curing of both natural rubber and other adhesives that were solvent coated on tape backings. Later references to electron beam curing... 

The Goodyear vulcanization process takes hours or even days to be produced. Accelerators can be added to reduce the vulcanization time. Accelerators are derived from aniline and other amines, and the most efficient are the mercaptoben-zothiazoles, guanidines, dithiocarbamates, and thiurams (Fig. 32). Sulphenamides can also be used as accelerators for rubber vulcanization. A major change in the sulphur vulcanization was the substitution of lead oxide by zinc oxide. Zinc oxide is an activator of the accelerator system, and the amount generally added in rubber formulations is 3 to 5 phr. Fatty acids (mainly stearic acid) are also added to avoid low curing rates. Today, the cross-linking of any unsaturated rubber can be accomplished in minutes by heating rubber with sulphur, zinc oxide, a fatty acid and the appropriate accelerator. 

It has been used to some extent as an ignition promotor for Diesel fuels, in insecticides, fungicides, as an accelerator in rubber vulcanization, and as an indicator in acid titrations (Refs 10 11)... 

Roseocobalt — see Cobalt, aquapentaammine-Roseopentaammine —see Aquapentaammine Roussin s black, 4, 1191 Roussin s red, 4, 1191 Roussin s salts, 4,240, 1243 Rubber vulcanization zinc complexes in, 5, 998 Rubeanic acid — see Dithiooxamid Rubidium complexes... 

Fig. 85.—Force-temperature curves at constant length obtained by Anthony, Gaston, and Guth for natural rubber vulcanized with sulfur for elongations from 3 percent to 38 percent (at 20°C), as indicated.

These conclusions have been confirmed by Wood and Roth, who carried out measurements at both constant lengths and at constant elongations using natural rubber vulcanized with sulfur and an accelerator. Their results at constant elongation, to be considered later in connection with the thermodynamics of rubber elasticity at higher elongations, are summarized in Fig. 89. 

Fig. 91.—(a) Schematic representation of cross-linking as in rubber vulcanization. (b) Incidence of cross-linked units within a given primary molecule. 

The equilibrium tension r at a = 2 for GR-S synthetic rubber vulcanized in this manner is plotted in Fig. 99 against the mole fraction (pXlOO) of units cross-linked. The straight line has been calculated... 

Similar results have been obtained for natural rubber vulcanized in like manner. Here also the observed equilibrium stress tends... 

The results of Cohan on the force of retraction r at a = 1.5 for GR-S synthetic rubbers vulcanized with various proportions of a calcium carbonate filler are shown in Fig. 104. The agreement with the theoretical curve drawn according to Eq. (52) is good. In further confirmation of the theory, variations in average particle diameter... 

Organic synthesis Sulfur mustard (HD) 1.18 Pharmaceuticals Sulfur dyes Insecticides Rubber vulcanization Polymerization catalyst Hardening of soft woods Extraction of gold from ores... 

Bis(nitrile oxides) obtained from dialkylbenzenes have been claimed as low-temperature rubber vulcanization agents (517). Curing of poly(butadiene-co-acrylonitrile) with 2,4,6-trimethylisophthalodinitrile N-oxide produces rubbery material of good quality, however, curing of (polybutadiene) was unsuccessful (518). The solubility of dinitrile oxides and stability of their ketone solutions has been studied for their application as vulcanizing agents in the production of mbberized materials (519). 

Borodachev IV, Volkhonskaya EV, Guk YuV, Zhukov AYu, Tsypin GI, Chernysheva SYu, Antipova VF, Panova NV. Bis(nitrile oxides) of dialkylbenzenes as low-temperature rubber vulcanization agents with low unsaturation and their manufacture from dialkylbenzenes, RU Patent No. 2042664 1995 [Chem. Abstr. 1996 124 263170],... 

Rubber, tellurium in, 24 427-428 Rubber, vulcanization of, 23 646 Rubbery plateau, 24 701 Rubella vaccine, 25 490-491 Rubiaceae... 

Workers in tire-manufacturing facilities may have a heightened potential for health hazards since the rubber vulcanization process can involve exposures to 77-hexane (Graham et al. 1995). 

ISO 188, Rubber, vulcanized or thermoplastic - Accelerated ageing and heat resistance tests (available in English only), 1998. 

ISO 1853, Conducting and dissipative rubbers, vulcanized or thermoplastic -Measurement of resistivity, 1998. 

ISO 2878, Rubber, vulcanized - Antistatic and conductive products -Determination of electrical resistance, 1987. 

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